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Daily useful information

During one day's work, many different on-line sources may be useful. Here goes the links that were useful to me! Let me know yours, especially if some of them are specific to your job or country!

Let's start with important data to keep in mind:

1 carat (ct) = 0,2 gram (g)

1 gram (g) = 5 carats (ct)

Some US companies, like auction houses, may give you the gross weight in pennyweights (dwt).

1 pennyweight (dwt) = 1.55517384 gram (g)


Converter from grams to carat: Metric Conversion

Old currency converter: here

Metal rates

Metal rate €urope: Cookson-CLAL

Metal rate in Dollar$ : Kitco


On-line very efficient translator: DeepL Translator

You may also use Chat GPT, but please be careful what data you are feeding it. It would be ill-advised to have him translate strategic data for example.

One must however be very careful and always have a native person proofread the document that you have translated with an on-line translator, specifically if it tackles technical subjects (manufacturing, contracts, etc.)

Hallmarks & Research

​Many interesting books that are no longer published today are still available, such as the French 'Guide Bijou', which can prove invaluable and a number of experts in the trade are able to carry out research, sometimes personnifying why I call the "Indiana Jones of the hallmark".

Also noteworthy, the École des Arts Joailliers published at the end of 2021 in partnership with Gallimard a reference work for professionals and amateurs of goldsmiths and jewellers: the Dictionnaire des joailliers, bijoutiers et orfèvres en France, de 1850 à nos jours. Sold at a price of €650 including tax, it can also be consulted at the School's library upon reservation or at the Union Syndicale, upon request. Unfortunately it is not available in English.

Your research are about coins ? Check your information there: Cosmos of Collectibles

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